Radio receiving system



Nov. 29, 1932. A. B. COLE 1,889,172

RADIO RECEIVING SYSTEM Filed Dec. 25, 1950 lNVENTOR H. B. Cale ATTORNEY Patented Nov. 29, 1932 PA; r

ARTHUR B. COLE, OF CALDVIELL, NEW JERSEY RADIO RECEIVING SYSTEM Application filed December 26, 1930. Serial No. 504,754.

I-Ieretofore many sets or systems of radio or wireless communication have utilized an overhead or elevated aerial or antenna for receiving electromagnetic waves, the disadvantages of which aerial are well known.

The object of my invention is to dispense with the aerials or antennae referred to and to provide simple and efficient wave receiving means, which may be connected to a receiving set and toground and may be retained entirely within a building, and thereby overcoming objections to outdoor aerials and reducing the cost of installation and.

maintenance of radio and wireless communicating sets.

In carrying out my invention I provide a connection to ground from the receiving terminal of a radio or wireless set and include in said connection a conductor, a suitable inductance and, preferably, a fixed condenser in series With said inductance, said connection or conductor with the inductance with or without the condenser, serving to receive electromagnetic waves for transmission to the appropriate element of the set, such as the primary of a radio frequency transformer whose secondary supplies potentials to the set, such as to the grid of an amplifier tube in a radio receiver.

Reference is to be had to accompanying drawings wherein Fig. 1 is a diagrammatic view illustrating my improvement in connection with a well known type of radio receiver;

Fig. 2 illustrates a modification, and

Fig. 3 illustrates another modification.

The numeral 1 indicates a binding post or receiving terminal adapted for connection with an aerial or antenna, and at 2 is a binding post for ground, or earth connection. 3 indicates the first or antenna radio frequency transformer whose primary 3a is connected with the posts 1 and 2. 4 indicates the first amplifier tube, 5 indicating its grid bias resistor, bypassed by the condenser 6. A second radio frequency transformer is indicated at 7, 8 indicates a second amplifier tube, and 9 indicates a third radio frequency transformer. Grid bias resistor for the tube 8 is indicated at 10, bypassed by the condenser former 3, is illustrated as connected to a conr 11. A detector tube is indicated at 12 and at 13 is an audio transformer. An audio amplifier tube is indicated at 14: connected with a loud-speaker or the like, at 15. 16 indicates the primary of a power transformer 17, whose several secondaries 18, 19and 20 sup ply various voltages for heating the tube filaments, the B potentials, and the filament of the rectifier tube 21, respectively.- Inductance 22, condensers 28, 24, and 26, r and resistor 27, include the conventional filtering and voltage dividing system commonly employed in so-called electric receivers. 28 indicates a grid bias resistor for the amplifier tube 1 1, the resistor being icy-passed C in an ordinary way by condenser 29.

The binding post or terminal 2, of primary 3a of the first radio frequency transductor as a common terminal for a considerable number of circuits. Such conductor may be the frame of the receiving set, and is illustrated at 30 as a conductor and is known as ground, connected to the earth terminal 2 of the receiver and to the several devices described, as shown. The parts described are well known in a typical form of electric radio receiver.

In accordance with my invention I pro vide, for receiving the earth component of the waves, aconnectionfrom the receiving binding post or terminal 1 to ground, indicated at 31, which may be a radiator, or any grounded pipe in a building or other place, or a conducting object buried in the earth, and said connection may comprise an insulated conductor 32 connected with post 1 and connecting with one terminal of an inductance 38, the opposite terminal of which inductance is connected in series to a terminal of a fixed condenser 34, the opposite terminal of which is connected to ground 31, as illustrated in Fig. 1. In Fig. 2 I have illustrated a modification in which the receiving connection from the post 1 to ground 31 includes the conductor .32 and inductance 33 without including the condenser 34.

In the example illustrated in Fig. 1 the circuit may be traced from ground or earth contact at 31 through the condenser 34:, in-

ductance 33 and conductor 32 to the binding post or terminal 1, thence to the primary 3a and post 2 to the common ground wire or frame 30, the circuitdividing at the point 35, one part passing through the condenser 52% to the secondary 20, another part passing through the condenser 29 to the secondary 18, and a third part passing to secondary 19 and thence from the secondaries 18, 19 and 20 to the primary 16 of the power transformer 17 and to the power lines 17, 17, one of which lines is generally grounded, or both of which usually have appreciable capacity to ground. The secondaries 18, 19 and 20, of the power transformer 16, are all connected to conductor 30, either-conductively or capacitatively. For example, secondary 19, which supplies high voltages to rectifier tube. 21,.has a centertap connection which is conductively joined to conductor 30 at any desired point in a known way. Secondary 18 supplies cur- .rent to thefilamentsof tubes 4, 8, .12 and 14%.

Fi 1 illustrates a commonl em lo ed a a n I u 1 1 means of obtaining grid blas for tne tunes, comprising the center tap connection of secondary 18, said center tap being connected to a resistor 28, which 1s by-passed by condenser 29 whose im edance to radlo fre uenc currents is purposely chosen to be low in value.

Thus, secondary 18 is capacitative y connected to conductor 30 by means of condenser 29,. Secondary 20is also capacitatively con nected to conductor 3.0 through condenserQ, which, being primarily employed in most radio sets as a filtering condenser to reduce the hum occasioned by the rectification of current bytube 21, has a very low impedance to radio frequency currents. In present standard makes of radio sets the power transformer has several secondary windings, one or more of which connecteither directly .or capacitatively with a conductor, su-ch as 30, to which conductor is also connected one terminal of the primary ofthe input transformer, such as 3a, so that a low impedance path to high frequency currents is provided from its input terminal to the several secondaries, such as 18, .19 and 20. The capacity between the secondaries 18 and QO'and the primary 16, is generally relatively small, so that the natural period of the circuit traced is high. The use of theinductance 33 and the condenser 34:, or of said inductance alone, raises such natural period .to a point determined by their values, preferably close to the range of wave lengths it is desired to receive. Furthermore, the use of the inductance 33, and the condenser 34, or said inductance alone, as described, reduces the coupling of the circuit with the secondary 3 of the transformer 3, thus rendering the recelver more selective in tuning. The prime advantage of using condenser 34: in conjunction with inductance 33, as compared with the use of inductance 33 alone, is that of obtaining sharpwithout the condenser.

ness of tuning with types of radio sets now in general use, which sharpness is equal to or better than that of the same sets when connected to the usual or overhead antenna system. This is accomplished by my invention through the selection of those values of inductance and capacity which so function best. In some designs of radio sets, however, it is unnecessary to obtain extreme degrees of sharpness of tuning in the antenna circuit, because of the sharpness obtained through succeeding amplifying stages in the set, due to the makers design. In connection with such sets, the use of inductance 33 alone, as illustrated in Fig. 2, has been found satisfactory.

The use of the inductance and the condenser as illustrated in Fig. 1, reduces the coupling of their circuit including the primary 3a with its secondary 3' to a greater degree than does the use of the inductance alone This reduction of coupling is well known in all high frequency magnetically coupled circuits.

While I have illustrated my invention in connection with'a typical form of radio receiver, practically all receivers are made with aerialand ground binding posts or terminals connected with the primary winding of a radio frequency transformer, and inithe socalled electric receivers the ground terminal is connected to the receiver frame or to a ground wire, such as at 30. With my improvement in use the complete circuit in any of such sets will be from ground, at '31,

through the condenser 34 and inductance 33,

(or through the inductance 33 alone), conductor 32,.primary'3a of the first radio frequency transformer, thence through the common ground, such as to frame or conductor30, and finally through capacity between one or more secondaries to the primary of a power transformer and out to the power line, to ground, hence my invention is not limited to use with-the particular radio receiver diagrammatically illustrated.

In order to provide a more definite capacity between conductor 30 and the power line I have illustrated, in Fig. 3, a condenser 36 connectedat one terminal by a conductor 37-with the conductor 30, and at the other terminal by a conductor 38 with one of the powerlines, such as at a terminal of primary 16,-to conductor 17 The condenser 36 may be used in a receiver such as described, in

An advantage of my invention is that the condenser 34 in series with the inductance 33 (or without the condenser 3a in series with said inductance) enables the use of a simple wave receiving device capable of being installed within a building or other place, and dispenses with an overhead outside aerial, thereby reducing the cost of such aerial and of its installation and maintenance, and the disadvantage that arises from the breaking down and the depreciation in wave-receiving value of the aerial due to weather conditions.

I am familiar with systems which use the electric supply line forpicking up the waves,

\ which are then fed to the input terminal of the set, but such an arrangement is not uniformly reliable in practice due to the widely varying radio frequency characteristics of electric supply lines, for when installed in iron conduits they have far greater capacity than when installed exposed without any containing pipe. My improvement is quite the reverse of the foregoing, namely, the energy is received at the ground terminal 31, is passed through inductance 33, or through condenser 34- and inductance 33, thence to input terminal 1, primary 3a, terminal 2 and through conductor to power line 17, thence to a different ground connection than 31, either by the deliberate grounding by the electric supply company of line 1'? or 17", or by the capacity between these lines and ground. My means of receiving the enrgy at a definite ground terminal has proven in practice more reliable than that of using the electric power lines as a collector.

Having now described my invention, what I claim is 1. A radio receiving system comprising i radio frequency input transformer, a condnctor connected with one terminal of the primary of said transformer, a power transformer having a plurality of sec ondaries connected with said conductor,

1 means to connect the primary of said power transformer to an electric supply line, and means connected with the other terminal of said first named primary for re ceiving electromagnetic waves including a conductor connected with the last named terminal of said primary, an inductance connected with said conductor, and means to connect said inductance to ground.

2. A radio receiving system comprising a radio frequency input transformer, a conductor connected with one terminal of the primary of said transformer, a power transformer having a plurality of secondaries connected with said conductor, means to connect the primary of said power transformer to an electric supply line, and means connected with the other terminal of said first named primary for receiving electromagnetic Waves, including a conductor connected with the last named terminal of said primary, an inductance connected with said conductor, a condenser connected in series with said inductance, and means to connect said inductance and condenser to ground;

3. A radio receiving system comprising a radio frequency input transformer, a conductor connected with one terminal of the primary of said transformer, a power transformer having a plurality of secondaries connected with said conductor, means to connect the primary of said power transformer to an electric supply line, and means connected with the other terminal of said first named primary for receiving electromagnetic waves, including a conductor connected with the last named terminal of said primary, an inductance connected with said conductor, means to connect said inductance to ground, a condenser connected to the first named conductor and means to connect said condenser to said electric supply line.

4. A radio receiving system comprising a radio frequency input transformer, a con-- ductor connected with one terminal of the primary of said transformer, a power transformer having a plurality of secondaries connected with said conductor, means to connect the primary of said power transformer to an electric supply line, and means connected with the other terminal of said first namedv primary for receiving electromagnetic waves, including a conductor connected with the last named terminal of said primary, an inductance connected with said conductor, a condenser connected in series with said inductance, means to connect said inductance and condenser to ground, a condenser connected to the first named conductor and means to connect said condenser to said electric supply line.

ARTHUR B. COLE. 

